The densities of cores from main hole (100 - 3000m) of Chinese Continental Scientific Drilling (SSCD) have been performed in the conditions of room temperature and pressure. The continuous section of densities from 100m to 3000m was constructed and densities of several kind of UHP rocks were constrained. Referring to the results of about 30 samples measured under high temperature (600 degrees C) and high pressure (600MPa), we found that the density of eclogite changes in this sequence 3.52 g/cm(3) -> 3.49 g/cm(3) -> 3.07 g/cm(3) -> 2.93 g/cm(3) while UHPM felsic rock changes as 3.00 g/cm(3) -> 2.80 g/cm(3) -2.65 g/cm(3), all in accordance with UHP rocks' retrogression. These results are the prerequisite parameters for the discussion of exhumation rate of UHP rocks. Based on the truth that the gravity, buoyant force is equal to viscous force while the exhumation block moves in balance, we did quantitative analysis of exhumation rate. According to the result, it is clear that the buoyancy associated with density contrast is the driven force for the UHP rock exhumation. Based on density contrast, temperature is the factor that influences the rate most. Density contrast exhumation angle and the volume of exhumation block are all important parameters for the construction of reasonable exhumation model. As the temperature drop from 850 degrees C to 700 degrees C, exhumation rate changes from 100mm/a to 1.51mm/a. So it is thought that in the early stage with high temperature UHP rocks move rapidly up to 60 similar to 70km, then as the temperature drops down, the blocks move slowly up to the middle-lower crust. Buoyancy is inferred to he the dominant. mechanism for the exhumation from deep mantle(> 100km) to lower crust(< 40km).